Myocardial ischemia-
reperfusion injury is associated with an imbalance between the formation and the scavenging of
reactive oxygen species. In this context, the protective role of the
antioxidant metallothionein, a thiol-rich
protein that is induced in different organs in response to
heavy metals and oxidative conditions, has mainly been investigated in
metallothionein-knockout mice or
metallothionein-overexpressing mice. The aim of this study was to evaluate whether the administration of
cadmium has a protective effect against cardiac
ischemia-reperfusion injury and whether this is associated with induction of in vivo cardiac
metallothionein. Forty-eight hours after an injection of 0, 1, or 2 mg/kg
cadmium, isolated perfused rat hearts were submitted to 30 min of total global
ischemia and 30 min of reperfusion. The
ischemia-reperfusion sequence was associated with a significant decrease in cardiac
metallothionein levels. Pretreatment with
cadmium at a dose of 2 mg/kg (i) prevented this decrease and (ii) improved the postischemic recuperation of the coronary flow, the ventricular developed pressure, and therefore, the global postischemic functional recovery. These results showed that pretreatment of rats with 2 mg/kg
cadmium induced cardioprotection against
ischemia-reperfusion injuries, perhaps through an in vivo
metallothionein induction that may be related to a
metal activation of
antioxidant systems.